1. Add pulpTunes and your browser (Safari, I guess) to Preferences -> Accounts -> Opening
2. In your browser, make your pulpTunes connection address your home page (will only work with
http://localhost:1500, unless you have a fixed IP or use a proxy)
3. In the pulpTunes settings, tell which playlist should be opened and check the 'Automatic play' box.
Restart your Mac and enjoy.

Note: I have a French system, so the names of the commands may vary in your language